PRODUCED BY A CONSTANT CURRENT. 39 



Experiment 27. 



+ P == 34 ; P =1653 Meidinger, Eh. 20 ; y 27. 



a. E = 33. The mechanical stimulus causes moderately strong 

 contractions ; the constant current neither make- nor break-con- 

 tractions. Under its influence, however, the contractions become 

 notably diminished, this decrease being less directly after the current 

 is closed than afterwards. After interruption of the current the 

 contractions return to their former strength and even go a little 

 beyond. 



b. E = 30. Under the influence of the same polarising current 

 the diminution of excitability takes almost the same course as in a ; 

 the increase of diminution attending the continuance of the current is 

 here quite clearly exhibited. 



c. E = 28-5. Here the diminution of excitability elicited by the 

 same polarising current is considerably less than in a and b ; all the 

 circumstances attending it, however, make their appearance here just 

 as much as in the foregoing series. 



d. E = 25-5. Here the polarising current causes a scarcely notice- 

 able diminution of the contractions. 



10. The change of position of the indifference-point with 

 increasing strength of a descending current. 



When I had convinced myself by means of the foregoing in- 

 vestigations that, up to the strongest polarising currents which 

 were at my disposal, there was in the intrapolar tract a decrease 

 of excitability at the positive, and an increase at the negative pole, 

 it became important to examine in what way different strengths 

 of current affected the relation between the length of the intrapolar 

 portion of nerve exhibiting increased excitability, and that of the 

 similar portion exhibiting decreased excitability ; or, in other 

 words, according to what law the indifference-point changed its 

 position with varying strengths of the polarising current. 



For this purpose I adopted the following procedure. I stimu- 

 lated a given spot lying at a certain distance from the negative 

 pole, and examined how the excitability there varied, when, begin- 

 ning with quite weak currents, I progressively increased their 

 strength. When I selected a spot not far from the negative pole, 

 these contractions exhibited in the first place an increase, which 

 became greater and greater the stronger the current used. When 

 however its strength was still further raised, there showed itself 

 instead a considerable diminution of the contractions. That this 



